[mem/{layout,memory_region,mgr}] removed kernel stack and boot stack

danbugs · danbugs · commit 02e3858c2fac · 2025-05-01T21:28:28.000Z
These memory regions were unused

Signed-off-by: danbugs &lt;danilochiarlone@gmail.com&gt;
diff --git a/src/hyperlight_host/src/mem/layout.rs b/src/hyperlight_host/src/mem/layout.rs
@@ -22,8 +22,8 @@ use rand::{rng, RngCore};
 use tracing::{instrument, Span};
 
 use super::memory_region::MemoryRegionType::{
-    BootStack, Code, GuardPage, GuestErrorData, Heap, HostExceptionData, HostFunctionDefinitions,
-    InputData, KernelStack, OutputData, PageTables, PanicContext, Peb, Stack,
+    Code, GuardPage, GuestErrorData, Heap, HostExceptionData, HostFunctionDefinitions, InputData,
+    OutputData, PageTables, PanicContext, Peb, Stack,
 };
 use super::memory_region::{MemoryRegion, MemoryRegionFlags, MemoryRegionVecBuilder};
 use super::mgr::AMOUNT_OF_MEMORY_PER_PT;
@@ -32,14 +32,6 @@ use crate::error::HyperlightError::{GuestOffsetIsInvalid, MemoryRequestTooBig};
 use crate::sandbox::SandboxConfiguration;
 use crate::{log_then_return, new_error, Result};
 
-// +-------------------------------------------+
-// |             Boot Stack (4KiB)             |
-// +-------------------------------------------+
-// |       Kernel Stack Guard Page (4KiB)      |
-// +-------------------------------------------+
-// |             Kernel Stack                  |
-// +-------------------------------------------+
-// |        Guest Stack Guard Page (4KiB)      |
 // +-------------------------------------------+
 // |             Guest (User) Stack            |
 // +-------------------------------------------+
@@ -71,10 +63,6 @@ use crate::{log_then_return, new_error, Result};
 // +-------------------------------------------+ 0x1_000
 // |                   PML4                    |
 // +-------------------------------------------+ 0x0_000
-// |                    ⋮                      |
-// |                 Unmapped                  |
-// |                    ⋮                      |
-// +-------------------------------------------+ 0x0
 
 ///
 /// - `HostDefinitions` - the length of this is the `HostFunctionDefinitionSize`
@@ -106,11 +94,6 @@ use crate::{log_then_return, new_error, Result};
 /// - `GuestPanicContext` - contains a buffer for context associated with any guest
 ///   panic that occurred.
 ///   the length of this field is returned by the `guest_panic_context_size()` fn of this struct.
-///
-/// Boot Stack - this is the stack that is used before the TSS is set up. It is fixed to 4K
-/// Kernel Stack Guard Page is to Guard against boot stack overflow so we dont corrupt the kernel stack
-/// Kernel Stack - this is the stack that is used for kernel mode operations we switch to this early in the initialization function
-/// Guest Stack Guard Page is to Guard against kernel stack overflow so we dont corrupt the user stack
 
 #[derive(Copy, Clone)]
 pub(crate) struct SandboxMemoryLayout {
@@ -147,12 +130,6 @@ pub(crate) struct SandboxMemoryLayout {
     guest_heap_buffer_offset: usize,
     guard_page_offset: usize,
     guest_user_stack_buffer_offset: usize, // the lowest address of the user stack
-    user_stack_guard_page_offset: usize,
-    kernel_stack_buffer_offset: usize,
-    kernel_stack_guard_page_offset: usize,
-    #[allow(dead_code)]
-    pub(super) kernel_stack_size_rounded: usize,
-    boot_stack_buffer_offset: usize,
 
     // other
     pub(crate) peb_address: usize,
@@ -263,22 +240,6 @@ impl Debug for SandboxMemoryLayout {
                 "Guest Code Offset",
                 &format_args!("{:#x}", self.guest_code_offset),
             )
-            .field(
-                "User Stack Guard Page Offset",
-                &format_args!("{:#x}", self.user_stack_guard_page_offset),
-            )
-            .field(
-                "Kernel Stack Buffer Offset",
-                &format_args!("{:#x}", self.kernel_stack_buffer_offset),
-            )
-            .field(
-                "Kernel Stack Guard Page Offset",
-                &format_args!("{:#x}", self.kernel_stack_guard_page_offset),
-            )
-            .field(
-                "Boot Stack Buffer Offset",
-                &format_args!("{:#x}", self.boot_stack_buffer_offset),
-            )
             .finish()
     }
 }
@@ -384,12 +345,6 @@ impl SandboxMemoryLayout {
         // round up stack size to page size. This is needed for MemoryRegion
         let stack_size_rounded = round_up_to(stack_size, PAGE_SIZE_USIZE);
 
-        let user_stack_guard_page_offset = guest_user_stack_buffer_offset + stack_size_rounded;
-        let kernel_stack_buffer_offset = user_stack_guard_page_offset + PAGE_SIZE_USIZE;
-        let kernel_stack_size_rounded = round_up_to(cfg.get_kernel_stack_size(), PAGE_SIZE_USIZE);
-        let kernel_stack_guard_page_offset = kernel_stack_buffer_offset + kernel_stack_size_rounded;
-        let boot_stack_buffer_offset = kernel_stack_guard_page_offset + PAGE_SIZE_USIZE;
-
         Ok(Self {
             peb_offset,
             stack_size: stack_size_rounded,
@@ -420,11 +375,6 @@ impl SandboxMemoryLayout {
             guard_page_offset,
             total_page_table_size,
             guest_code_offset,
-            user_stack_guard_page_offset,
-            kernel_stack_buffer_offset,
-            kernel_stack_guard_page_offset,
-            kernel_stack_size_rounded,
-            boot_stack_buffer_offset,
         })
     }
 
@@ -591,22 +541,6 @@ impl SandboxMemoryLayout {
         self.get_min_guest_stack_address_offset() + size_of::<u64>()
     }
 
-    /// Get the offset of the kernel stack pointer in guest memory,
-    #[instrument(skip_all, parent = Span::current(), level= "Trace")]
-    fn get_kernel_stack_pointer_offset(&self) -> usize {
-        // The kernelStackAddress is immediately after the
-        // userStackAddress in the `GuestStackData` struct which is a `u64`.
-        self.get_user_stack_pointer_offset() + size_of::<u64>()
-    }
-
-    /// Get the offset of the boot stack pointer in guest memory,
-    #[instrument(skip_all, parent = Span::current(), level= "Trace")]
-    fn get_boot_stack_pointer_offset(&self) -> usize {
-        // The bootStackAddress is immediately after the
-        // kernelStackAddress in the `GuestStackData` struct which is a `u64`.
-        self.get_kernel_stack_pointer_offset() + size_of::<u64>()
-    }
-
     // Get the offset in guest memory to the start of the guest panic context data
     #[instrument(skip_all, parent = Span::current(), level= "Trace")]
     pub(crate) fn get_guest_panic_context_offset(&self) -> usize {
@@ -644,7 +578,7 @@ impl SandboxMemoryLayout {
     /// layout.
     #[instrument(skip_all, parent = Span::current(), level= "Trace")]
     fn get_unaligned_memory_size(&self) -> usize {
-        self.get_boot_stack_buffer_offset() + PAGE_SIZE_USIZE
+        self.get_top_of_user_stack_offset() + self.stack_size
     }
 
     /// get the code offset
@@ -660,34 +594,6 @@ impl SandboxMemoryLayout {
         Self::BASE_ADDRESS + self.guest_code_offset
     }
 
-    /// Get the offset in guest memory to the user stack guard page
-    /// This is the offset in the sandbox memory where the user stack guard page starts
-    #[instrument(skip_all, parent = Span::current(), level= "Trace")]
-    pub(super) fn get_user_stack_guard_page_offset(&self) -> usize {
-        self.user_stack_guard_page_offset
-    }
-
-    /// Get the offset in guest memory to the kernel stack buffer
-    /// This is the offset in the sandbox memory where the kernel stack starts
-    #[instrument(skip_all, parent = Span::current(), level= "Trace")]
-    pub(super) fn get_kernel_stack_buffer_offset(&self) -> usize {
-        self.kernel_stack_buffer_offset
-    }
-
-    /// Get the offset in guest memory to the kernel stack guard page
-    /// This is the offset in the sandbox memory where the kernel stack guard page starts
-    #[instrument(skip_all, parent = Span::current(), level= "Trace")]
-    pub(super) fn get_kernel_stack_guard_page_offset(&self) -> usize {
-        self.kernel_stack_guard_page_offset
-    }
-
-    /// Get the offset in guest memory to the boot stack buffer
-    /// This is the offset in the sandbox memory where the boot stack starts
-    #[instrument(skip_all, parent = Span::current(), level= "Trace")]
-    pub(super) fn get_boot_stack_buffer_offset(&self) -> usize {
-        self.boot_stack_buffer_offset
-    }
-
     #[cfg(test)]
     /// Get the page table size
     fn get_page_table_size(&self) -> usize {
@@ -971,80 +877,12 @@ impl SandboxMemoryLayout {
         }
 
         // stack
-        let user_stack_guard_page_offset = builder.push_page_aligned(
+        let final_offset = builder.push_page_aligned(
             self.get_guest_stack_size(),
             MemoryRegionFlags::READ | MemoryRegionFlags::WRITE,
             Stack,
         );
 
-        let expected_user_stack_guard_page_offset =
-            TryInto::<usize>::try_into(self.get_top_of_user_stack_offset())?
-                + self.get_guest_stack_size();
-
-        if user_stack_guard_page_offset != expected_user_stack_guard_page_offset {
-            return Err(new_error!(
-                "User Guard Page offset does not match expected User Guard Page offset expected:  {}, actual:  {}",
-                expected_user_stack_guard_page_offset,
-                user_stack_guard_page_offset
-            ));
-        }
-
-        let kernel_stack_offset = builder.push_page_aligned(
-            PAGE_SIZE_USIZE,
-            MemoryRegionFlags::READ | MemoryRegionFlags::STACK_GUARD,
-            GuardPage,
-        );
-
-        let expected_kernel_stack_offset =
-            TryInto::<usize>::try_into(self.kernel_stack_buffer_offset)?;
-
-        if kernel_stack_offset != expected_kernel_stack_offset {
-            return Err(new_error!(
-                "Kernel Stack offset does not match expected Kernel Stack offset expected:  {}, actual:  {}",
-                expected_kernel_stack_offset,
-                kernel_stack_offset
-            ));
-        }
-
-        let kernel_stack_guard_page_offset = builder.push_page_aligned(
-            self.kernel_stack_size_rounded,
-            MemoryRegionFlags::READ | MemoryRegionFlags::WRITE,
-            KernelStack,
-        );
-
-        let expected_kernel_stack_guard_page_offset =
-            TryInto::<usize>::try_into(self.kernel_stack_guard_page_offset)?;
-
-        if kernel_stack_guard_page_offset != expected_kernel_stack_guard_page_offset {
-            return Err(new_error!(
-                "Kernel Guard Page offset does not match expected Kernel Guard Page offset expected:  {}, actual:  {}",
-                expected_kernel_stack_guard_page_offset,
-                kernel_stack_guard_page_offset
-            ));
-        }
-
-        let boot_stack_offset = builder.push_page_aligned(
-            PAGE_SIZE_USIZE,
-            MemoryRegionFlags::READ | MemoryRegionFlags::STACK_GUARD,
-            GuardPage,
-        );
-
-        let expected_boot_stack_offset = TryInto::<usize>::try_into(self.boot_stack_buffer_offset)?;
-
-        if boot_stack_offset != expected_boot_stack_offset {
-            return Err(new_error!(
-                "Boot Stack offset does not match expected Boot Stack offset expected:  {}, actual:  {}",
-                expected_boot_stack_offset,
-                boot_stack_offset
-            ));
-        }
-
-        let final_offset = builder.push_page_aligned(
-            PAGE_SIZE_USIZE,
-            MemoryRegionFlags::READ | MemoryRegionFlags::WRITE,
-            BootStack,
-        );
-
         let expected_final_offset = TryInto::<usize>::try_into(self.get_memory_size()?)?;
 
         if final_offset != expected_final_offset {
@@ -1187,17 +1025,9 @@ impl SandboxMemoryLayout {
 
         // The top of the user stack is calculated as the size of the guest memory + the guest offset which gives us the
         // address at the bottom of the guest memory.
-        // we then subtract the size of the stack, the size of the kernel stack,
-        // the size of the boot stack, the size of the user stack guard page and the size of the kernel stack guard page
-        // which are all 4K
 
         let bottom = guest_offset + size;
-        let min_user_stack_address = bottom
-            - self.stack_size
-            - self.kernel_stack_size_rounded
-            - PAGE_SIZE_USIZE
-            - PAGE_SIZE_USIZE
-            - PAGE_SIZE_USIZE;
+        let min_user_stack_address = bottom - self.stack_size;
 
         // Top of user stack
 
@@ -1212,26 +1042,6 @@ impl SandboxMemoryLayout {
 
         shared_mem.write_u64(self.get_user_stack_pointer_offset(), start_of_user_stack)?;
 
-        // Start of kernel stack
-
-        // There is a guard page between the user stack and the kernel stack and then we need to add the size of the kernel stack
-
-        let start_of_kernel_stack: u64 =
-            start_of_user_stack + (PAGE_SIZE_USIZE + self.kernel_stack_size_rounded) as u64;
-
-        shared_mem.write_u64(
-            self.get_kernel_stack_pointer_offset(),
-            start_of_kernel_stack,
-        )?;
-
-        // Start of boot stack
-
-        // There is a guard page between the kernel stack and the boot stack and then we need to add the size of the boot stack
-
-        let start_of_boot_stack: u64 = start_of_kernel_stack + (PAGE_SIZE_USIZE * 2) as u64;
-
-        shared_mem.write_u64(self.get_boot_stack_pointer_offset(), start_of_boot_stack)?;
-
         // End of setting up the PEB
 
         // Initialize the stack pointers of input data and output data
@@ -1306,14 +1116,6 @@ mod tests {
 
         expected_size += round_up_to(layout.stack_size, PAGE_SIZE_USIZE);
 
-        expected_size += PAGE_SIZE_USIZE; // user stack guard page
-
-        expected_size += round_up_to(layout.kernel_stack_size_rounded, PAGE_SIZE_USIZE);
-
-        expected_size += PAGE_SIZE_USIZE; // kernel stack guard page
-
-        expected_size += PAGE_SIZE_USIZE; // boot stack
-
         expected_size
     }
 
diff --git a/src/hyperlight_host/src/mem/memory_region.rs b/src/hyperlight_host/src/mem/memory_region.rs
@@ -149,10 +149,6 @@ pub enum MemoryRegionType {
     GuardPage,
     /// The region contains the Stack
     Stack,
-    /// The region contains the Kernel Stack
-    KernelStack,
-    /// The region contains the Boot Stack
-    BootStack,
 }
 
 /// represents a single memory region inside the guest. All memory within a region has
diff --git a/src/hyperlight_host/src/mem/mgr.rs b/src/hyperlight_host/src/mem/mgr.rs
@@ -58,7 +58,7 @@ const PAGE_USER: u64 = 1 << 2; // User/Supervisor (if this bit is set then the p
 const PAGE_NX: u64 = 1 << 63; // Execute Disable (if this bit is set then data in the page cannot be executed)
 
 // The amount of memory that can be mapped per page table
-pub(super) const AMOUNT_OF_MEMORY_PER_PT: usize = 0x200000;
+pub(super) const AMOUNT_OF_MEMORY_PER_PT: usize = 0x200_000;
 /// Read/write permissions flag for the 64-bit PDE
 /// The page size for the 64-bit PDE
 /// The size of stack guard cookies
@@ -213,8 +213,6 @@ where
                             // Host Exception Data are readonly in the guest
                             MemoryRegionType::HostExceptionData => PAGE_PRESENT | PAGE_NX,
                             MemoryRegionType::PageTables => PAGE_PRESENT | PAGE_RW | PAGE_NX,
-                            MemoryRegionType::KernelStack => PAGE_PRESENT | PAGE_RW | PAGE_NX,
-                            MemoryRegionType::BootStack => PAGE_PRESENT | PAGE_RW | PAGE_NX,
                         },
                         // If there is an error then the address isn't mapped so mark it as not present
                         Err(_) => 0,
